Localization in Clinical Neurology Part 1 Flashcards
__ sulcus divides the frontal and parietal lobe
Anterior is the ___ gyrus, contains the primary __ cortex
Posterior is the __ __ gyrus which has the primary __ cortex
Each person has a dominant and non dominant hemisphere
- __ has pathways responsible for language and praxis
- __ __ has pathways for visual and spatial perception and attention.
RHand dom people are 95% of the __ __. People who are LHand dominant are only 60% left hemisphere dominant.
Central sulcus divides the frontal and parietal lobe
Anterior is the precentral gyrus, contains the primary motor cortex
Posterior is the post central gyrus which has the primary sensory cortex
Each person has a dominant and non dominant hemisphere
- Dominant has pathways responsible for language and praxis
- Non dom has pathways for visual and spatial perception and attention.
RHand dom people are 95% of the Left hemisphere. People who are LHand dominant are only 60% left hemisphere dominant.
Brain stem: contains the __, __ and __.
Brain stem: contains the midbrain, pons and medulla.
Below the cerebral cortex and deep to the nuclei are white matter tracts. One important WM tract is the __ ___, where all the descending motor capsule and all sensory fibers run together in a compact space.
Below the cerebral cortex and deep to the nuclei are white matter tracts. One important WM tract is the internal capsule, where all the descending motor capsule and all sensory fibers run together in a compact space.
Corticospinal tract
Starts in the __ __ cortex in pre central gyrus. UMN makeup grey matter.
Arranged in motor homunculus– face and arm neurons more __, and the leg tracts more __.
These tracts of the homunculus descend into the brain in a fan-like shape called the __ __
These fibers converge at the _ _, and descend along the __ brainstem until they reach the bottom of the __, at which point they cross down the contralateral side and descend along the spinal cord.
When they reach the appropriate level, they synapse with the motor neuron, and the MN exits at the __ cord. Multiple motor neurons can come together and form a __ outside of the spinal cord.
Upper limb= __ plexus
Lower limb= __ plexus.
Several nerves come out from the plexus containing fibers from multiple nerve roots. These nerves communicate through the neuromuscular junction with the muscles.
Corticospinal tract
Starts in the primary motor cortex in pre central gyrus. UMN makeup grey matter.
Arranged in motor homunculus– face and arm neurons more laterally, and the leg tracts more medially.
These tracts of the homunculus descend into the brain in a fan-like shape called the corona radiata
These fibers converge at the internal capsule, and descend along the IPSILATERAL brainstem until they reach the bottom of the medulla, at which point they cross down the contralateral side and descend along the spinal cord.
When they reach the appropriate level, they synapse with the motor neuron, and the MN exits at the ventral cord. Multiple motor neurons can come together and form a plexus outside of the spinal cord.
Upper limb= brachial plexus
Lower limb= lumbosacral plexus.
Several nerves come out from the plexus containing fibers from multiple nerve roots. These nerves communicate through the neuromuscular junction with the muscles.
Pathology affecting any part of the corticospinal tract will produce weakness:
If UMN: weakness is UMN in nature, and will have associated __, __ deep tendon reflexes and __ plantar response as well as __ pattern of weakness; __ muscles are weaker than _ muscles in the upper extremity, which causes the __ __. In the lower extremities during a cortical pattern of weakness, the flexors are weaker than the extensors.
If LMN is affected: weakness is in the LMN in nature, and will have associated __, __, decreased tone, decreased deep tendon reflexes, a downgoing plantar reflex, as well as various patterns of weakness depending on which level is affected.
Pathology affecting any part of the corticospinal tract will produce weakness:
If UMN: weakness is UMN in nature, and will have associated spasticity, increased deep tendon reflexes and outgoing plantar response as well as cortical pattern of weakness; extensor muscles are weaker than flexor muscles in the upper extremity, which causes the pronator drift. In the lower extremities during a cortical pattern of weakness, the flexors are weaker than the extensors.
If LMN is affected: weakness is in the LMN in nature, and will have associated atrophy, fasciculations, decreased tone, decreased deep tendon reflexes, a downgoing plantar reflex, as well as various patterns of weakness depending on which level is affected.
Lesions of the corticospinal tract
A lesion involving PMC will cause __ ___ weakness, but given the sheer size of the motor homunculus, it is unlikely that a lesion would affect the face, arm and legs neurons equally.
- Due to the blood supply of the hemisphere, the face and arm are often weaker than the leg during a __ cerebral artery stroke. The leg is weaker in the setting of an __ cerebral artery stroke.
A lesion involving the _corona radiata t_racts (where the tracts are converging to the internal capsule) will produce __ __-_ weakness. varying amounts in limbs.
Lesion at the internal capsule will produce __ __ weakness of the __=__=__ because the tracts are in super close proximity to each other, making the lesion affecting the tracts the same amount.
Lesion in the spinal cord will often result in __ __ below the level of the lesion.
Disorders that affect the motor neurons (Lou Gehrig’s disease) affect __ and ___ and will therefore produce a mixed picture of UMN and LMN weakness.
A lesion affecting a single nerve root will cause an ___ ___ neuron weakness affecting all muscles within that __.
A plexus lesion in each limb is complicated. Lesion of a plexus will cause Ipsilateral motor neuron weakness affecting the entire limb, and the weakness is not contained within a single myotome, as multiple nerves are potentially affected and thus different muscular compartments of the limb.
A lesion involving PMC will cause contralateral UMN weakness, but given the sheer size of the motor homunculus, it is unlikely that a lesion would affect the face, arm and legs neurons equally.
- Due to the blood supply of the hemisphere, the face and arm are often weaker than the leg during a middle cerebral artery stroke. The leg is weaker in the setting of an anterior cerebral artery stroke.
A lesion involving the _corona radiata t_racts (where the tracts are converging to the internal capsule) will produce contralateral hemi-UMN weakness. varying amounts in limbs.
Lesion at the internal capsule will produce EQUAL contralateral weakness of the F=A=L because the tracts are in super close proximity to each other, making the lesion affecting the tracts the same amount.
Lesion in the spinal cord will often result in bilateral weakness below the level of the lesion.
Disorders that affect the motor neurons (Lou Gehrig’s disease) affect UMN and LMN and will therefore produce a mixed picture of UMN and LMN weakness.
A lesion affecting a single nerve root will cause an ipsilateral motor neuron weakness affecting all muscles within that myotome.
A plexus lesion in each limb is complicated. Lesion of a plexus will cause Ipsilateral motor neuron weakness affecting the entire limb, and the weakness is not contained within a single myotome, as multiple nerves are potentially affected and thus different muscular compartments of the limb.
compared to demyelination and axonal peripheral neuropathies which often work distal>proximal, disorders that affect the NMJ often cause symmetrical ___>____ LMN
proximal>distal
the spinothalamic Tract
- a sensory pathway responsible for perception of __ and __.
Receptors detect pain and temp, relaying it to the first order peripheral nerve.
The first order nerve synapses on the second order neuron at the __ __ __, which __ __ and ascends the spinal cord on the contralateral side and brain stem until it reaches the __
At the thalamus the second order neuron synapses with the third order neuron, where it __ up to the __ __ via the ___ __.
the spinothalamic Tract
- a sensory pathway responsible for perception of pain and termperature.
Receptors detect pain and temp, relaying it to the first order peripheral nerve.
The first order nerve synapses on the second order neuron at the dorsal nerve root, which crosses over and ascends the spinal cord on the contralateral side and brain stem until it reaches the thalamus
At the thalamus the second order neuron synapses with the third order neuron, where it ascends up to the sensory cortex via the corona radiata.
Each level of the spinothalamic tract has different characteristics that can air in localization:
Disorders of a single peripheral nerve can lead to specific distal areas having a loss of pain and temperature sensation→ __, such as in carpal tunnel
Disorders affecting multiple nerves can produce a polyneuropathy pattern that looks like a __-__ pattern→ seen in diabetes.
- Feet are first affected, when it reaches the knees (stocking), the hands start having pain and temp sensation loss (glove)
- If someone has stocking-glove pattern (ie in diabetes), consider more of a peripheral nerve problem first
__ __ patterns; various single nerves around the body are affected and can lead to chaotic and random pain and temperature sensation loss around the body.
When a __ is affected; chaotic sensory loss in a single limb that does not fit in a single dermatome
__; will result in sensory loss affecting a single __.
__ cord lesions; sensory level loss of sensation __ that level
Lesions within brain stem; __ loss (__ sensory pattern) where pain and tmep sensation are loss on the __ face and __ body
Thalamus lesion; __ loss
Corona radiata lesion; varying degrees in contralateral sensory loss depending on lesion location
Disorders of a single peripheral nerve can lead to specific distal areas having a loss of pain and temperature sensation→ mononeuropathy, such as in carpal tunnel
Disorders affecting multiple nerves can produce a polyneuropathy pattern that looks like a stocking-glove pattern→ seen in diabetes.
- Feet are first affected, when it reaches the knees (stocking), the hands start having pain and temp sensation loss (glove)
- If someone has stocking-glove pattern (ie in diabetes), consider more of a peripheral nerve problem first
Mononeuritis multiplex patterns; various single nerves around the body are affected and can lead to chaotic and random pain and temperature sensation loss around the body.
When a plexus is affected; chaotic sensory loss in a single limb that does not fit in a single dermatome
Radiculopathy; will result in sensory loss affecting a single dermatome.
Spinal cord lesions; sensory level loss of sensation below that level
Lesions within brain stem; hemisensory loss (cross sensory pattern) where pain and tmep sensation are loss on the ipsilateral face and contralateral body
Thalamus lesion; hemisensory loss
Corona radiata lesion; varying degrees in contralateral sensory loss depending on lesion location
the Dorsal Column Pathway is responsible for detecting vibtation and proprioception
Receptors relay along the peripheral nerve, goes through the plexus, and enter the __ __. From the __ __, it goes up the __ spine into the top of the __.
At the __, the first order neuron synapses on 2nd order, which promptly __ _ and ascends up the __ __ __
From the BS, it goes to the __. Within the __, the 2nd order neuron synapses at 3rd order neuron, which sends fibers that traverse the __ __ to the corresponding location on the PSC.
the Dorsal Column Pathway is responsible for detecting vibtation and proprioception
Receptors relay along the peripheral nerve, goes through the plexus, and enter the dorsal root. From the dorsal root, it goes up the ipsilateral spine into the top of the medulla.
At the medulla, the first order neuron synapses on 2nd order, which promptly crosses over and ascends up the contralateral brain stem.
From the BS, it goes to the thalamus. Within the thalamus, the 2nd order neuron synapses at 3rd order neuron, which sends fibers that traverse the corona radiata to the corresponding location on the PSC.
Putting the three pathways all together: NOTES
Every level of the NS does not function in isolation.
A lesion affecting the PMC and sensory cortex will produce contralateral hemiUMN weakness of varying patterns depending on where the lesion is on the homunculus, with face and arm being affected more than leg, and vice versa, patients will often have corresponding hemisensory deficits if the lesion crosses posteriorly into the central sulcus and sensory cortex.
Because these lesions are affecting the cortex, lesions of the PMC or PSC will produce cortical signs, including aphasia (if the dominant hemisphere is affected), or hemi-neglect (if the non-dominant side is lesioned)
Lesions affecting the corona radiata look similar to those of PMC and PSC with contralateral hemi UMN weakness of varying distributions, but NO CORTICAL SIGNS
Lesions of internal capsule will produce contralateral hemiUMN weakness or sensory loss, but the weakness of the F=A=L WILL ALL BE EQUAL since the tracts are so close together (unlike in lesions of the PMC/PSC/CR)
If sensory fibers are affected, there will be contralateral hemisensory loss
Lesions of the thalamus do not affect the CST, and will not produce weakness, but only hemisesnory loss.
Lesions can also cause cortical signs (weird)
Brain stem lesions will cause EQUAL F=A=L or bilateral weakness of UMN.
Cross sensory pattern may be seen.
These patients will have true cranial nerve signs and symptoms
Spinal cord lesions cause bilateral UMN weakness and sensory loss below the level of the lesion
- Autonomic dysfunction common (loss of bowel and bladder control)
Beware of brown sequard syndrome; ipsilateral weakness and vibration loss, and contralateral pain and temperature loss below the level of the lesion.
Motor Neuron Disorders; mix of UMN and LMN weakness. No sensory or autonomic symptoms. Weakness in isolation
Radiculopathies; ipsilateral myotome LMN weakness and dermatome sensory loss
Plexus; chaos in one limb. LMN weakness and sensory loss that doesn’t fit in a single nerve root distribution.
Peripheral nerve pathology; mononeuropathy (LMN weakness in a single distribution), or polyneuropathy (distal>proximal LMN weakness with corresponding stocking-glove sensory loss).
NMJ disorders; no sensory loss, only LMN fatiguable weakness
Myopathies; no sensory loss, only symmetric proximal>distal LMN weakness.
There are specific myopathies where proximal muscles are not affected to a greater extent that distal
Cerebellar lesion; ipsilateral ataxia.
Basal ganglia pathology; movement disorders like parkinsons or huntingtons.
Description and Sensory and motor findings for these syndromes
Localization Investigations:
Are there any other signs/symptoms?
- Sensory deficits?
- If no, chances are you’re dealing with levels of the __ that do not involve the sensory system; muscle, __ and __ __ disorder. There are some __ though that are an exception.
If yes, then look at the pattern.
- Cranial nerve signs?
What CN sense is affected and thus which level of the brainstem is affected?
CN signs are __ (cranial nerves are LMN)
Look for signs of __ or __ cortical signs that may indicate which hemisphere is affected (nondominant or dominant). Look for ANS dysfunction, or ataxia which might indicate a cerebellar or basal ganglia issue (hypo/hyperkinetic movement disorder)
Localization Investigations:
Are there any other signs/symptoms?
- Sensory deficits?
- If no, chances are you’re dealing with levels of the LMN that do not involve the sensory system; muscle, NMJ and motor neuron disorder. There are some polyneuropathies though that are an exception.
If yes, then look at the pattern.
- Cranial nerve signs?
What CN sense is affected and thus which level of the brainstem is affected?
CN signs are ipsilateral
Look for signs of neglect or aphasia cortical signs that may indicate which hemisphere is affected (nondominant or dominant). Look for ANS dysfunction, or ataxia which might indicate a cerebellar or basal ganglia issue (hypo/hyperkinetic movement disorder)
brown sequard syndrome; __ weakness and vibration loss, and __ pain and temperature loss below the level of the lesion.
brown sequard syndrome; ipsilateral weakness and vibration loss, and contralateral pain and temperature loss below the level of the lesion.
Caused by a spinal cord lesion.
oultine the etiologic ddx: VITAMIN CDEF for localization of lesions
